Very good point. Indurance for me is key. The older I get (I'm 55) the slower I "bounce back" so indurance helps me build a strength base so I dont get hurt. Though not always as fun as getting the burdt from the intervals. Thanks for advice.Though I've been cycling for many years (road and mtn, as well as Peloton), I've also had to stop temporarily from time to time due to injuries and surgeries. Based on my experience of getting back into shape, I'm going to suggest something a bit different in response to your question. When trying to get into (or back into) shape, I've found it to be important to build up endurance - the length of each class you take - before increasing the intensity through HITT or Tabata rides. 15 minute rides are a great start, but my suggestion is to continue with Low Impact rides until you can do them for 30 minutes. You might also want to check out the Power Zone beginner/endurance rides for a change up. Once you can do 30 minutes reasonably without too much difficulty or discomfort, then start including some more intense rides like HITT and Tabata. For me a 15 minute HITT or Tabata ride is not for beginners and instead is for more advanced riders who have limited time and want a very intense short workout. Just my two cents. Congrats and good luck!